1. Field of the Invention
The present invention relates to PWM power regulators and/or DC—DC converters, and more particularly to precision margining circuitry used to validate performance and reliability of system cards during manufacturing testing.
2. Description of the Related Art
Voltage margin circuitry used in power regulators allow for the raising and lowering of the output voltage relative to a nominal value. In many cases, voltage margining is used to validate performance and reliability of a system during manufacturing testing for quality control, such as computer motherboards, system peripheral cards, etc. In other cases, margining may be used to adjust the balance between performance and product lifetime. For example, performance may be increased by increasing voltage and/or clock rate of a system (e.g., computer graphics card), at the cost of reduced lifetime of the product. Alternatively, the clock and/or voltage may be reduced to increase life expectancy at reduced performance levels.
Many conventional techniques have been employed to implement margining, including physical component changes, external switches, etc. Such techniques were often inefficient and usually inaccurate. Margining circuitry often consumed valuable board space and/or consumed valuable time during manufacturing testing. Different manufacturers employ different margining specifications, which have been difficult to achieve using present techniques. One margining technique employed internal current sources to develop the margining voltage. Such current sources varied significantly (e.g. 10%) over process and temperature changes, resulting in substantial loss of precision. A dedicated pin had to be added to the integrated circuit (IC) to perform a reduction in set point error. Additional dedicated pins are not favored by IC designers and are avoided as often as possible.
It is desired to increase margining set point precision without the cost of additional pins to the part.